Straubel / AP Biology 2012 -2013



Succession POGIL answer keyBarren No There is no soil, only rock, so roots would not be able to take hold and there is also a lack of nutrients Small ferns, mosses and lichensSeed blown by the wind, dropped by birds, etc. Diagram BLow nutrient requirements, small or low growing shallow roots systems Taller plants can receive more sunlight and shade out smaller plants therefore decreasing the competition. More sunlight would increase the rate of photosynthesis helping the plant grow The number of pioneer organisms because they are struggling to survive As the plant dies out, they decay and enrich the composition of the soil, adding humus and nutrients. Grazing animals would leave footprints for the seeds to lie in and leave manure to fertilize the seeds. They consume early pioneer species to make room for the next colonizers and aid in seed dispersal The level of grazing can impact any further succession as the animals eat the young plant shoots Primary succession in the successive rise and fall of population of plants from original colonizers to mature trees and shrubs, beginning with barren rock that has no initial soil layer The trees are taller so they can out-compete other plants for light, they are slower growing so they can withstand short term changes in conditions Temperature, amount of light and length of day and water availability. The climax community A fire has burned the forest and destroyed it Natural lightning or man started the fire The process of succession will have to start over again Yes evidence is provided in diagram F, where once again a climax community is establishedThere is no colonizing by lichens and mosses as soil or some other substrate is already present. This speeds up the recovery time from hundreds of years to tens of years Because the already present climax community was set back by the fire and is starting form an area with soil rather than starting from a barren land Primary succession Secondary succession Secondary succession Primary succession Not always. Man is responsible for deforestation by cutting down trees for lumber or land development Forest managements, controlled burning, managed animal grazing Selective logging will open up small spaces for light penetration, which allows existing saplings to grow rapidly and fill in the gaps. Clear cutting of large areas will open up land and begin the process of full decondary succession so the area will take longer to regenerate. ................
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